High all , just wanted to say Menards has 4X8 white plastic sheeting its about 1/8th an inch thick and has like a plastic inside glued inbetween two fairly solid plastic sheeting outsides . its near the 1/4 inch panaling and sheeting, around the plywoods.
Ohh and Home Depot doesnt seem to carry it here anyway Lowes may though not sure?
They actually wanted like double at a grow shop around here for the same exact stuff from Menards!
From the side it looks like cardboard but a little thicker and all plastic. I think i paid around 15-18 bucks. for a 4X8 Then i just cut it to fit nice, it has one side with faint lines to help in cutting and the other is a duller flat white.I also cut 2 pieces about 4" wide one the length of the tray, the other 4" by the width of tray.I Cut a slot in one of these and slide the other into it, making a sort of cross. Very important tho ya have to cut at least a few areas away from the side of the insert that is going to be resting on the tray to allow the water to flow under the stabalizing insert. This goes in the tray to help support the cover from underneth, once all the plants weigh on it sometimes it may sag a little but taping around the edges helps that a little too.
This stuff is deffinitly the best stuff ive found it is tough stuff, can be used more than once, Totally washable and its affordable too!!
Last i just drill it with a hole saw and drop in net pots, a little tape around them, the heavy duty duct normally will stick for an entire cycle easy.
Anyway i know im rambling but i hope i was of some help..
If anyone else has found anything else good or great, and its fairly affordable id love to hear..
I know it really isnt necessary and i can make it tougher to get in and out of.. but not really too much in my opinion, when all the pots are taped in its easy to either untape individual ones, or just the tray top real quick and just pick up.
Peace Nickel